I have the Injen meant for the Versa - I would suggest getting the HKS though as I had to cut in to the hood, and even then it rubbed, so I've now gone to a smaller filter. Sitting on top of the battery just doesn't seem like the best place, and it'd be easier to build a heat shield than to tin-snip the hood.
You won't have issue with warranty unless it's "related", Canada has quite a bit of precedent even without the magnus act. Your wheel bearing isn't effected by your intake etc. If you were to have intake issues... just save the old intake and swap it back? I still have all my stock components (but that's for fixing any issues on another micra).
I tend not to accelerate hard from stops, usually maxing out around 3K due to noise. If I'm doing a road trip or something I do my best to keep it efficient... but there are several fun chicanes near my house, both on and off ramps, a few short on and off ramps with next to no run off so I get some good cornering fun out of it. I definitely bring it up to 5K in a few sections somewhat regularly, and I have to swap out my cat before I can really determine if I've got a leak in the exhaust side anywhere as there's been a smell recently. That'll be in the next two weeks.
View my fuel log 2015 Micra SV automatic: 7.1 L/100 km ... 39.9 mpg (Imp) ... 14.1 km/L ... 33.3 mpg (US) ...